Equipment for use in harvesting grain has gone from primitive hand-held tools to sophisticated self-propelled combines in the past 150 years. The size and capacities of harvesting machines have increased as technology has improved. At present, the headers of commercially-available combines are believed to have maximum widths of approximately 30 feet, but there are indications that for greater operating efficiencies many farmers would prefer headers of even greater width. Unfortunately, size increases are commonly associated with problems that offset the advantages of greater efficiency. For example, a commercial 30 foot combine header must be removed from the combine and either trailed behind the unit or hauled on a separate vehicle in order to maintain a suitable width for safe road travel. Such detachment and reattachment is time consuming, presents some risk of injury to the operators during detachment, attachment, loading, and unloading, and involves additional expenses for a trailer or separate vehicle. Another problem that increases with greater header size involves adaptation to uneven terrain. A rigid header of 30 feet in width may conform poorly with changes in terrain, and may become unyieldly and virtually inoperative in traversing terraced or rolling terrain.
Efforts have been made to provide headers which overcome such problems, but such efforts have met with only limited success. U.S. Pat. No. 3,345,808 discloses a harvester having a header divided into a pair of hinged sections that may be raised into generally vertical positions during transport. When the sections are so raised, they generally obstruct the driver's view of the road, and if the header width were increased to take advantage of the collapsing or retracting feature, then the raised sections might also present special problems in traveling beneath bridges, power lines, and other overhead obstructions. Even when the sections are in lowered operative positions, the hinged construction is not free of serious shortcomings. In FIG. 1 of the patent, the header is shown traversing crested terrain; however, as the combine travels over level terrain, and especially as it traverses depressions and concavities that cause the free ends of the hinged sections to swing upwardly, the header will necessarily leave a substantial uncut center swath.
Other patents illustrative of the state of the art are U.S. Pat. Nos. 4,184,314, 4,204,575, 3,897,832, 4,047,575, 4,178,009, 4,249,616, 4,206,815, 4,042,044, 4,084,394, and 4,151,886.